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SubjectRe: system hung up when offlining CPUs
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On 09/16/2017 11:02 AM, Thomas Gleixner wrote:
> On Sat, 16 Sep 2017, Thomas Gleixner wrote:
>> On Thu, 14 Sep 2017, YASUAKI ISHIMATSU wrote:
>>> Here are one irq's info of megasas:
>>>
>>> - Before offline CPU
>>> /proc/irq/70/smp_affinity_list
>>> 24-29
>>>
>>> /proc/irq/70/effective_affinity
>>> 00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,3f000000
>>>
>>> /sys/kernel/debug/irq/irqs/70
>>> handler: handle_edge_irq
>>> status: 0x00004000
>>> istate: 0x00000000
>>> ddepth: 0
>>> wdepth: 0
>>> dstate: 0x00609200
>>> IRQD_ACTIVATED
>>> IRQD_IRQ_STARTED
>>> IRQD_MOVE_PCNTXT
>>> IRQD_AFFINITY_SET
>>> IRQD_AFFINITY_MANAGED
>>
>> So this uses managed affinity, which means that once the last CPU in the
>> affinity mask goes offline, the interrupt is shut down by the irq core
>> code, which is the case:
>>
>>> dstate: 0x00a39000
>>> IRQD_IRQ_DISABLED
>>> IRQD_IRQ_MASKED
>>> IRQD_MOVE_PCNTXT
>>> IRQD_AFFINITY_SET
>>> IRQD_AFFINITY_MANAGED
>>> IRQD_MANAGED_SHUTDOWN <---------------
>>
>> So the irq core code works as expected, but something in the
>> driver/scsi/block stack seems to fiddle with that shut down queue.
>>
>> I only can tell about the inner workings of the irq code, but I have no
>> clue about the rest.
>
> Though there is something wrong here:
>
>> affinity: 24-29
>> effectiv: 24-29
>
> and after offlining:
>
>> affinity: 29
>> effectiv: 29
>
> But that should be:
>
> affinity: 24-29
> effectiv: 29
>
> because the irq core code preserves 'affinity'. It merily updates
> 'effective', which is where your interrupts are routed to.
>
> Is the driver issuing any set_affinity() calls? If so, that's wrong.
>
> Which driver are we talking about?

We are talking about megasas driver.
So I added linux-scsi and maintainers of megasas into the thread.

Thanks,
Yasuaki Ishimatsu

>
> Thanks,
>
> tglx
>

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